19 



amount of either acid or alkali. The solution is not coagu- 

 lated by heat. The albuminate is completely precipitated 

 when the solution is neutralized. "A solution in dilute acid is 

 completely precipitated by saturation with ammonium sul- 

 phate or sodium chloride, while the solution in alkali is not 

 precipitated by similar treatment. 



Syntonin, formed during gastric digestion, is an important 

 example of acid albumin or albuminate. 



18. Albuminates. — Action of acids and alkalies on albumin. 

 Take three test-tubes and label them A, B, C. In each, place 

 an equal amount of diluted egg-white, like that used at the 

 last exercise. To A add a few drops of 0.1 % solution of caustic 

 potash. To B add the same amount of 0.1% solution of caustic 

 potash. To C add a rather larger amount of 0.2% hydrochloric 

 acid, (6.5 cc. concentrated acid to 1 liter of water). 



Put all three into a warm water bath at about the temper- 

 ature of the body (36-40 C). 



19. After ten or fifteen minutes remove test tube A and 

 boil. The proteid is no longer coagulated by heat, having 

 been converted into alkali- albumin. After cooling, color with 

 litmus solution, and neutralize with 0.2% acid by the contact 

 method. At the neutral point a precipitate is formed, which 

 is soluble in excess of either acid or alkali. Quite as delicate 

 a test may be obtained without the litmus by means of the 

 contact method. A distinct white precipitate appears between 

 the two layers of fluid. 



20. Next remove B. This also now contains alkali-albu- 

 min. Add to it a few drops of a sodium phosphate solution, 

 color with litmus, and neutralize as before. Note that the 

 alkali-albumin now requires more acid for its precipitation 

 than in A, the acid which is first added converting the sodium 

 phosphate into acid sodium phosphate. 



21. Now remove C from the bath. Boil it. Again there 

 is no coagulation, the proteid having been converted into acid- 

 albuminum or syntonin. After cooling color with litmus and 

 neutralize with 0.1% alkali. At the neutral point a precipi- 

 tate is formed soluble in excess of acid or alkali. (Acid-albu- 

 min is formed more slowly than alkali-albumin, so that it is 

 well to take plenty of time). 



